title: Photorefractive keratectomy. A 6-year follow-up study.
abstract: OBJECTIVE
  This study aimed to assess the long-term stability and efficacy of excimer laser photorefractive keratectomy.
  
  
  METHODS
  Patients who participated in the first United Kingdom photorefractive keratectomy clinical trial were asked to attend a 6-year follow-up assessment.
  
  
  METHODS
  Eighty-three patients (68%) of the original cohort of 120 participants were observed for 6 years. A Summit Technology UV200 excimer laser with a 4-mm ablation zone had been used with patients allocated to one of six groups according to their preoperative refraction. Each group received one of the following spherical corrections: -2, -3, -4, -5, -6, or -7 diopters (D). Within each group, all patients received an identical treatment, and thus emmetropia was not the goal in all patients.
  
  
  METHODS
  The induced refractive change, objective corneal haze, glare, and halo measurements, together with possible late-phase complications, were analyzed.
  
  
  METHODS
  All groups achieved a refractive undercorrection, and the magnitude of the undercorrection was related to the size of the attempted correction. The induced refraction stabilized by 6 to 12 months and has been maintained up to the 6-year follow-up stage.
  
  
  RESULTS
  Ninety-one percent of patients who underwent a -2.00-D correction and 76% of patients who received a -3.00-D correction were within +/- 1 D of the intended refraction at 6 years. Fifty-seven percent of the -4.00-D group and 50% of those in the -5.00-D group were within +/- 1 D, and this was reduced further to 43% in the -6.00-D group and 19% in the -7.00-D group. Six patients (7%) had evidence of residual corneal haze, which was visually significant in two patients (3%). Ten patients (12%) had significant night halos due to the small 4-mm ablation zone that was used in this early treatment trial.
  
  
  CONCLUSIONS
  There was no further regression of the refraction after 1 year, and, more important, there was no sign of hyperopic shift or diurnal fluctuation in the patients' refraction. In addition, corneal haze appeared to reduce further with time, with no intraocular or retinal side effects being noted. Night halos remain a significant reported problem in a small number of patients who were treated with the 4-mm ablation zone.
authors.affiliation: Department of Ophthalmology, St. Thomas' Hospital, London, England.
authors.forename: C G
authors.initials: CG
authors.lastname: Stephenson
authors.forename: D S
authors.initials: DS
authors.lastname: Gartry
authors.forename: D P
authors.initials: DP
authors.lastname: O'Brart
authors.forename: M G
authors.initials: MG
authors.lastname: Kerr-Muir
authors.forename: J
authors.initials: J
authors.lastname: Marshall
mesh_terms: D000328:Adult; D003315:Cornea / Q000503:physiopathology / Q000601:surgery*; D003318:Corneal Opacity / Q000209:etiology / Q000503:physiopathology; D005500:Follow-Up Studies; D006801:Humans; D007429:Intraocular Pressure; D054018:Lasers, Excimer; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D018903:Photorefractive Keratectomy / Q000009:adverse effects; D011183:Postoperative Complications; D016896:Treatment Outcome; D014792:Visual Acuity / Q000502:physiology